The invention relates to a fuel injection system for an internal-combustion engine particularly a diesel engine, having a crankcase and at least one cylinder head, having fuel injectors for injecting fuel into the combustion spaces of the internal-combustion engine and a common rail supplied with fuel by a high-pressure pump, by which common rail the fuel is fed to the injectors by way of a high-pressure line system.
In the case of internal-combustion engines, particularly large-volume diesel engines, fuel injection systems are used which comprise fuel injectors for injecting fuel into the combustion spaces of the internal-combustion engine, and a so-called common rail which is supplied with fuel by a high-pressure pump, the fuel being supplied by the common rail by way of high -pressure lines to the injectors.
It is generally endeavored to construct internal-combustion engines and their fuel-injection systems in a simpler manner, and to design them to be more maintenance-friendly and less susceptible to disturbances.
From European Patent Document EP 0690 221 A1, a fuel injection system for an internal-combustion engine is known which comprises fuel injectors for injecting fuel into the combustion spaces and a common rail which is supplied with fuel by a high-pressure pump and which supplies fuel by way of high-pressure lines to the injectors. In this case, the common rail is integrated in the wall of a cylinder head cover arranged on the internal-combustion engine. In the above-mentioned document, it is considered to be advantageous that the manufacturing and mounting expenditures are reduced and the common rail is arranged to be protected against vibrations and damage. However, it seems to be a disadvantage that a demounting of the cylinder head cover is not possible without detaching the high-pressure lines connected with the common rail.
Furthermore, from German Patent Document DE-GM 75 15 413, an internal-combustion engine is known which has a fuel injection system in the case of which all ducts required for the guiding of fuel are arranged in a parallel extending manner in an extruded profile, the extruded profile being a component of the engine casing or of the cooling air guiding system. As a result, an operationally reliable, space-saving and easily mountable arrangement of the fuel pipes is to be created. However, here also, it seems to be a disadvantage that, in the event of a demounting of the engine casing or of the cooling air guiding system, which may be required for servicing work, all connections of the fuel ducts to the extruded profile must also be disconnected.
From European Patent Document EP 0637 687 A1, an internal-combustion engine is known in which, for the feeding of fuel to individual injection pumps constructed in the form of plug-type pumps, ducts in the form of bores used as a fuel advancing flow device and as a fuel returning flow device are provided in the cylinder housing of the internal-combustion engine. However, these fuel ducts are used only for the feeding and removal of the fuel to and from the plug-type pumps. However, this is no injection system with a common rail.
Finally, from U.S. Pat. No. 3,845,748, an internal-combustion engine is known in the case of which a fuel injector is arranged in a first bore in the cylinder head of the internal-combustion engine and a tube leading to the fuel injector is arranged for feeding fuel in a second bore leading through the cylinder head, which bore extends at a right angle to the first bore. A ring-shaped space remaining between the fuel feeding tube and the interior wall of the second bore is used as a fuel return device.
It is an object of the invention to provide a fuel injection system for an internal-combustion engine which has a simple construction, is safe in the event of an accident and has a low susceptibility to disturbances.
This object is achieved by providing a fuel injection system with the common rail arranged to be accommodated in or on walls of the crankcase. The fuel injection system according to the invention is provided for an internal-combustion engine, particularly a diesel engine, in which case the internal-combustion engine has a crankcase and one or several cylinder heads. The fuel injection system has fuel injectors for injecting fuel into the combustion spaces of the internal-combustion engine and a common rail supplied with fuel by a high-pressure pump, by which common rail the fuel is supplied by way of a high-pressure line system to the injectors. According to the invention, it is provided that the common rail is accommodated in a duct which is formed at least partially by walls of the crankcase.
It is an advantage of the fuel injection system according to the invention that, as the result of the accommodation of the common rail system according to the invention, a compact method of construction of the internal-combustion engine is permitted. The accommodation in the area of the crankcase does not interfere very much with the course of the contour of the internal-combustion engine and does not limit the narrow space in the area of the cylinder head. The injection system, in particular, is also well protected against outside damage.
According to a further development of the invention, the common rail is arranged in a duct integrated in the crankcase and extending in parallel to the longitudinal axis of the crankcase or is accommodated in a duct formed by the crankcase walls and a charge air tube. As a result, a smooth outer contour of the internal-combustion engine can be implemented without disturbing lines.
According to a further development, the common rail has a tube-shaped construction.
A further development of the invention is particularly advantageous in which the tube-shaped common rail is arranged in a longitudinal bore extending in parallel to the longitudinal axis of the crankcase. In a simple manner, this permits a precisely fitting bearing of the common rail in the radial and axial direction, in which case the common rail can particularly be disposed to be protected from vibrations.
Here, it is particularly advantageous to dispose the tube-shaped common rail, for example, by means of O-rings, in the longitudinal bore. This type of bearing is simple, precisely fitting and protected against vibrations.
It is particularly advantageous to arrange the common rail to be closed off with respect to liquids in the crankcase of the internal-combustion engine.
This is advantageously further developed in that the duct accommodating the common rail forms a liquid-tight leakage chamber which is provided with devices for removing leakage quantities.
In this embodiment, the leakage chamber is advantageously provided with a control bore for indicating the occurring leakage quantities.
In combination with the arrangement of the common rail, it is particularly advantageous to accommodate also the high-pressure lines connecting the injectors with the common rail and the injectors themselves in a closed-off manner in the casing of the internal-combustion engine. This results in a complete protection of the whole injection system against damage by outside influences and permits a completely smooth outer contour of the internal-combustion engine without any lines or projecting parts.
The closing-off of the high-pressure line system advantageously takes place by its arrangement in bores provided in the cylinder head.
The two latter embodiments are advantageously further developed in that the common rail is arranged close to the cylinder head in the crankcase, and in that the common rail has high pressure connections which are accessible through mounting openings provided in the crankcase and/or in the cylinder head, to which high-pressure connections the high-pressure lines are connected which lead to the injectors. In this case, it is particularly advantageous for the mounting openings to be arranged such that the high-pressure connections as well as the injectors and the high-pressure lines are accessible and mountable through these mounting openings. This permits an advantageous reduction of the mounting and servicing expenditures.
The mounting openings can be closed either by closing covers, or the cylinder head can be constructed in several parts, such that the mounting openings are closed by an easily demountable part of the cylinder head.
According to a particularly advantageous embodiment, a charge air tube provided at the internal-combustion engine is constructed as this above-mentioned, easily demountable part of the cylinder head. In this case, it is particularly advantageous for the mounting openings to be provided laterally on the cylinder head and to close them by means of the charge air tube.
Advantageously, the mounting openings and air inlet ducts leading from the charge air tube to the combustion spaces of the internal-combustion engine are arranged essentially in a row in a sealing surface between the cylinder head and the charge air tube. This significantly simplifies the manufacturing of the openings and sealing surfaces on the cylinder head and on the charge air tube. Furthermore, it can be provided and is particularly advantageous in the case of this embodiment that the mounting openings and the air inlet ducts on the sealing surface are sealed off by a common seal.
It is the advantage of the above-mentioned embodiments, in which the mounting openings are closed off by the charge air tube, that no additional mounting covers and fastening parts are required, and that, when an individual cylinder head is exchanged, only the charge air tube and the high-pressure line leading to the injector of the concerned cylinder head must be detached and the common rail and the other high-pressure lines do not have to be demounted.
A further development is particularly advantageous in which the charge air tube has a drain duct, which extends in parallel to the longitudinal crankcase axis, for the accommodation of leakage and control fuel quantities occurring at the injectors, into which drain duct the leakage and control fuel ducts lead which extend to the injectors. This can be further developed such that the leakage and control fuel ducts are connected with the bores accommodating the injectors, in which case the injectors are constructed such that they deliver the leakage and fuel quantities into the bores. This results in a further simplification of the fuel injection system.
In this case, it is advantageous for the leakage and control fuel ducts to extend through the sealing surface containing the mounting openings and to seal them off in the sealing surface by the seal which seals off the mounting openings and the charge air tube with respect to one another.
According to an embodiment, it is provided that the common rail, for the connection of a line leading to the high-pressure pump and/or of a pressure sensor, extends at least at one end out of the crankcase. In this case, it is advantageous to connect the line leading to the high-pressure pump and the pressure sensor on the same end of the common rail.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.